1. Field of the Invention
The present invention generally relates to a timing pulse generating apparatus, and more particularly to a timing pulse generating apparatus for generating a variety of timing pulses used for acquiring image signals from a solid-state imaging device.
2. Description of Related Art
A conventional timing pulse generating apparatus comprises a counter that produces address data by counting reference clocks in one frame period and a read only memory (a ROM) that stores data (signal level is xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d) for generating timing pulses for one frame period. To generate the timing pulses, the timing pulse generating apparatus successively reads data whose signal level is xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d from the ROM in accordance with the address data produced by the counter.
To generate one timing pulse on one screen of a solid-state imaging device whose horizontal number of pixels is 780 and vertical number of pixels is 520, the ROM requires a capacity of 50 kilobyte, which is arrived at by multiplying 780 by 525 and dividing the product by 8. A plurality of timing pulses is required to drive the solid-state imaging device, and the solid-state imaging device has a plurality of drive modes such as a drive mode for normal shooting, a drive mode for animations and a drive mode for auto focusing. Therefore, the ROM requires a capacity of at least 1 megabyte, which is arrived at by multiplying 50 kilobyte by the number of the types of the pulses and multiplying the product by the number of the modes, and the capacity of the ROM must be large as a result.
Japanese Patent Provisional Publication No. 9-205591 discloses a timing pulse generating circuit that reduces the capacity of the ROM. The timing pulse generating circuit stores in the ROM only data representing change points of the timing pulses and periods when the data is kept, and controls reading the data from the ROM to generate the timing pulses. In the case of this timing pulse generating circuit, however, the more change points the timing pulses have, the more data the ROM has to store, and the data stored in the ROM is required for the number of the modes. Moreover, horizontal timing pulses are not always the same at all the vertical lines, and thus it is required to generate a plurality of timing pulses and select only desired timing pulses in accordance with the positions of the lines. Therefore, the timing pulse generating circuit is complicated.
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of a timing pulse generating apparatus that can remarkably reduce the amount of data used for generating timing pulses and can reduce the cost of a storing device for storing the data.
To achieve the above-described object, the present invention is directed to a timing pulse generating apparatus which generates a variety of timing pulses used for acquiring image signals from a solid-state imaging device, the timing pulse generating apparatus comprising: a horizontal counter which counts reference clocks, a count value of the horizontal counter being reset in synchronization with a horizontal synchronous signal; a storing device which stores pattern data for generating the timing pulses, the pattern data comprising data representing timing pulses for one period first generated in a horizontal scanning period and repeat times of the timing pulses for one period in the horizontal scanning period; a pattern data setting device which reads the pattern data corresponding to desired timing pulses from the storing device and sets the read pattern data in a horizontal register; and a timing pulse generating device which generates and outputs the timing pulses in accordance with the count value of the horizontal counter and the pattern data set in the horizontal register.
According to the present invention, the timing pulses are generated in accordance with the pattern data representing the timing pulses for one period first generated in the horizontal scanning period and the repeat times of the timing pulses for one period in the horizontal scanning period. Therefore, the amount of the pattern data is small even if the repeat times of the timing pulses for one period in the horizontal scanning period are large.
To achieve the above-described object, the present invention is directed to a timing pulse generating apparatus which generates a variety of timing pulses used for acquiring image signals from a solid-state imaging device in accordance with pattern data representing timing pulses set in a horizontal register, the timing pulse generating apparatus comprising: a vertical counter which counts clocks synchronous with a horizontal synchronous signal, a count value of the vertical counter being reset in synchronization with a vertical synchronous signal; a first storing device which stores a plurality of pieces of pattern data for generating a plurality of types of timing pulses; a second storing device which stores mode data in accordance with a plurality of drive modes of the solid-state imaging device, the mode data representing names of patterns in the pattern data arranged in a predetermined order in one of one field and one frame to output at least one type of timing pulses and vertical switch positions where the timing pulses corresponding to the names of the patterns are switched; a mode data setting device which reads the mode data from the second storing device in accordance with the drive mode of the solid-state imaging device and sets the read mode data in a vertical register; and a pattern data setting device which reads the pattern data from the first storing device in accordance with the count value of the vertical counter and the mode data set in the vertical register and sets the pattern data in the horizontal register.
According to the present invention, the mode data is read from the second storing device in accordance with the drive mode of the solid-state imaging device and set in the vertical register. The mode data comprises the data representing the names of the patterns in the pattern data arranged to output one or more types of the timing pulses in the predetermined order in one field or frame and the vertical switch positions where the patterns are switched.
Thus, the timing pulses are switched at appropriate vertical positions in accordance with the mode data set in the vertical register, and the amount of the data can be small since the pattern data stored in the first storing device are commonly used even if there are a lot of modes.
To achieve the above-described object, the present invention is directed to a timing pulse generating apparatus which generates a variety of timing pulses used for acquiring image signals from a solid-state imaging device, the timing pulse generating apparatus comprising: a horizontal counter which counts reference clocks, a count value of the horizontal counter being reset in synchronization with a horizontal synchronous signal; a first storing device which stores pattern data for generating the timing pulses, the pattern data comprising data representing timing pulses for one period first generated in a horizontal scanning period and repeat times of the timing pulses for one period in the horizontal scanning period; a vertical counter which counts clocks synchronous with a horizontal synchronous signal, a count value of the vertical counter being reset in synchronization with a vertical synchronous signal; a second storing device which stores mode data in accordance with a plurality of drive modes of the solid-state imaging device, the mode data representing names of patterns in the pattern data arranged in a predetermined order in one of one field and one frame to output at least one type of timing pulses and vertical switch positions where the timing pulses corresponding to the names of the patterns are switched; a mode data setting device which reads the mode data from the second storing device in accordance with the drive mode of the solid-state imaging device and sets the read mode data in a vertical register; a pattern data setting device which reads the pattern data from the first storing device in accordance with the count value of the vertical counter and the mode data set in the vertical register and sets the pattern data in the horizontal register; and a timing pulse generating device which generates and outputs the timing pulses in accordance with the count value of the horizontal counter and the pattern data set in the horizontal register.
Preferably, the data representing the timing pulses for one period first generated in the horizontal scanning period comprise data representing a start level at a start of the horizontal scanning period, a position of a first change point where a signal level first changes from the start level, a position of a second change point where the signal level returns to the start level after passing the first change points, and a pattern length which is a length of one period of the timing pulses. This reduces the amount of the pattern data.
Preferably, the timing pulse generating device generates the timing pulses for one period by setting a signal level to the start level at the start of the horizontal scanning period, then reversing the signal level from the start level when the count value of the horizontal counter reaches the first change point represented with the pattern data, then setting the signal level to the start level when the count value of the horizontal counter reaches the second change point represented with the pattern data, and then maintaining the signal level until the count value of the horizontal counter reaches the pattern length, and the timing pulse generating device generates the timing pulses for one period the repeat times represented with the pattern data.
Preferably, the pattern data setting device sets, at the start of one vertical scanning, the pattern data corresponding to a name of a first pattern in the mode data set in the vertical register, and performs, in the order of the names of the patterns in the mode data, setting the pattern data corresponding to the name of the next pattern in the mode data set in the vertical register when the count value of the vertical counter reaches the next vertical switch position.
Preferably, the mode data setting device comprises: a mode name setting device which sets a name of a mode in a mode register in accordance with a drive mode of the solid-state imaging device at each vertical synchronous period; and a mode data reading device which reads the mode data from the second storing device in accordance with the name of the mode set in the mode register.